Abstract
The effects of three relevant organic pollutants: chlorpyrifos (CPF), a widely used insecticide, triphenyl phosphate (TPHP), employed as flame retardant and as plastic additive, and bisphenol A (BPA), used primarily as plastic additive, on sea urchin (Paracentrotus lividus) larvae, were investigated. Experiments consisted of exposing sea urchin fertilized eggs throughout their development to the 4-arm pluteus larval stage. The antioxidant enzymes glutathione reductase (GR) and catalase (CAT), the phase II detoxification enzyme glutathione S-transferase (GST), and the neurotransmitter catabolism enzyme acetylcholinesterase (AChE) were assessed in combination with responses at the individual level (larval growth). CPF was the most toxic compound with 10 and 50% effective concentrations (EC10 and EC50) values of 60 and 279 μg/l (0.17 and 0.80 μM), followed by TPHP with EC10 and EC50 values of 224 and 1213 μg/l (0.68 and 3.7 μM), and by BPA with EC10 and EC50 values of 885 and 1549 μg/l (3.9 and 6.8 μM). The toxicity of the three compounds was attributed to oxidative stress, to the modulation of the AChE response, and/or to the reduction of the detoxification efficacy. Increasing trends in CAT activity were observed for BPA and, to a lower extent, for CPF. GR activity showed a bell-shaped response in larvae exposed to CPF, whereas BPA caused an increasing trend in GR. GST also displayed a bell-shaped response to CPF exposure and a decreasing trend was observed for TPHP. An inhibition pattern in AChE activity was observed at increasing BPA concentrations. A potential role of the GST in the metabolism of CPF was proposed, but not for TPHP or BPA, and a significant increase of AChE activity associated with oxidative stress was observed in TPHP-exposed larvae. Among the biochemical responses, the GR activity was found to be a reliable biomarker of exposure for sea urchin early-life stages, providing a first sign of damage. These results show that the integration of responses at the biochemical level with fitness-related responses (e.g., growth) may help to improve knowledge about the impact of toxic substances on marine ecosystems.
Highlights
A variety of biological measures can potentially be used to evaluate the risk of damage caused by environmental pollutants to marine ecosystems, as long as they fulfill three fundamental conditions that allow obtaining relevant results at the ecosystem level: (i) to be standardizable, rapid, and cost-effective; (ii) to be sufficiently sensitive to the toxic effect of pollutants; and (iii) to have implications on the biological fitness of the individual (Stebbing et al 1980; Rand et al 1995; Calow 1998)
It has been recommended that enzymatic biomarkers of exposure, representing compensatory responses of the organism (Campillo et al 2013; Regoli and Giuliani 2014; Quetglas-Llabrés et al 2020), should be used in combination with biomarkers of effect (Bocquené and Galgani 1998; Campillo et al 2013; Vidal-Liñán and Bellas 2013), that may help to understand the potential consequences of these alterations on the health status of the organisms (Viarengo et al 2007)
CPF, bisphenol A (BPA), and triphenyl phosphate (TPHP) affected the embryonic development of the sea urchin P. lividus within the experimental concentration range in a dose-dependent manner (Figure 1, Figure S1)
Summary
A variety of biological measures can potentially be used to evaluate the risk of damage caused by environmental pollutants to marine ecosystems, as long as they fulfill three fundamental conditions that allow obtaining relevant results at the ecosystem level: (i) to be standardizable, rapid, and cost-effective; (ii) to be sufficiently sensitive to the toxic effect of pollutants; and (iii) to have implications on the biological fitness of the individual (e.g., mortality, growth, reproduction, feeding rates) (Stebbing et al 1980; Rand et al 1995; Calow 1998). The application of biomarkers in laboratory and field studies, including large-scale monitoring programs, has revealed their main weakness which is the limited knowledge of their ecological significance regarding the structure and function of the population or ecosystem (Bellas et al 2014; Campillo et al 2019), since the mechanistic link with individual- or population-level responses is usually not straightforward (Maltby et al 2001) In this respect, it has been recommended that enzymatic biomarkers of exposure (e.g., the antioxidant enzymes glutathione reductase and catalase or the phase II detoxification enzyme glutathione S-transferase), representing compensatory responses of the organism (Campillo et al 2013; Regoli and Giuliani 2014; Quetglas-Llabrés et al 2020), should be used in combination with biomarkers of effect (e.g., indicators of damage such as the neurotransmitter catabolism enzyme acetylcholinesterase) (Bocquené and Galgani 1998; Campillo et al 2013; Vidal-Liñán and Bellas 2013), that may help to understand the potential consequences of these alterations on the health status of the organisms (Viarengo et al 2007)
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